| In this paper,medium-maturation(Bulang)plum fruits were used as materials.Firstly,the effects of salicylic acid(SA)treatment on chilling injury and quality of plum fruits were studied,and the mechanism of improving the cold resistance about SA treatment from the ascorbate-glutathione(ASA-GSH)cycle and osmolytes of plum fruits.Then,the effect of ethylene(ET)signals involved in SA to improve cold resistance of postharvest plum fruits was explored.Finally,The role of cyanide-resistant respiration in the process of ET signals involved in SA to improve cold resistance of postharvest plum fruits was studied.The main research results show as follow:Firstly,The effect of SA on improving cold resistance of postharvest plum fruits.The results showed that SA treatment could delay the maturity and senescence of plum fruits under low temperature storage conditions,significantly delay the rise of titratable acid and reducing sugar content,maintain the higher osmotic adjustment substances of plum fruits.In addition,SA treatment of plum fruits significantly increased the activity of antioxidant enzymes in the ASA-GSH cycle,eliminated excess H2O2 in time,reduced the degree of peroxidation of plum membrane lipids,At the same time,guaranteed the regeneration of ascorbic acid(ASA)and reduced glutathione(GSH)and the normal operation of the ASA-GSH circulation system,and enhanced cold resistance of plum fruit.Secondly,The effect of ET signal involved in SA to improve cold resistance of postharvest plum fruits.The results showed that SA treatment significantly reduce the chilling injury rate and chilling injury index,delay the increase of peroxidase(POD)and polyphenol oxidase(PPO)activity,delay flesh browning,mitigate chilling injury symptoms.Moreover,it could also augment the activities of superoxide dismutase(SOD)and catalase(CAT),and maintain lower levels of cell membrane permeability and malondialdehyde(MDA).Thereby,it had a certain inhibitory effect on the occurrence of cell membrane lipid peroxidation.In addition,SA treatment also significantly increased the activity of phenylalanine ammonia lyase(PAL)and maintained a high total phenol content of fruit.The experiment also found that ET treatment significantly inhibited the occurrence of chilling injury in the early and middle of storage,SA combined with 1-methylcyclopropene(1-MCP)treatment significantly inhibited the occurrence of chilling injury in the middle of storage,but the accumulation rate of chilling injury was higher both treatments than that of SA treatment,and 1-MCP treatment accelerated the accumulation of chilling damage.The above results indicate that the appropriate concentration of exogenous SA treatment can enhance the cold resistance of plum fruit after harvest,and ethylene signal participates in the process,but it is not a dependent factor.Thirdly,The effect of cyanide-resistant respiration in the process of ET signals involved in SA to improve cold resistance of postharvest plum fruits.The results showed that SA treatment and 1-MCP combined with pyruvate treatment significantly reduced the chilling injury rate and chilling injury index of plum fruits,delay the increase of browning enzyme activity,significantly improve the reactive oxygen species(ROS)metabolism of fruits,maintain lower levels of MDA.In addition,Both treatments significantly inhibited the ethylene release of plum fruits and delayed the emergence of respiratory jump peaks.Among them,1-MCP combined with pyruvate treatment also delayed the fruit ethylene jump during storage.The experiment also found that ET treatment significantly inhibited the occurrence of chilling injury in the early and middle of storage,SA combined with ET treatment significantly inhibited the occurrence of chilling injury in the early stage of storage,SA combined with salicylhydroxamic acid(SHAM)treatment significantly inhibited the occurrence of chilling injury in the early and middle of storage,but the accumulation rate of chilling injury was higher three treatments than that of SA treatment and 1-MCP combined with pyruvate treatment,and ET combined with SHAM treatment accelerated the accumulation of chilling damage.The above results indicate that SA treatment partially inhibits the ET signal,and cyanide-resistant respiration may be involved in the interaction of salicylic acid and ethylene during cold induction.It is speculated that SA may induce cyanide-resistant respiration in plum fruits,Thereby improving the cold resistance of plum fruit. |
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